Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

126
FXUS63 KLOT 021132
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
632 AM CDT Tue Jun 2 2026

.KEY MESSAGES...

- Generally dry conditions through mid-week with seasonable
  temperatures inland and cooler conditions near the lake.

- Rain chances return Friday and may linger through the weekend.

&&

.DISCUSSION...
Issued at 130 AM CDT Tue Jun 2 2026

Sprawling ~1030 mb high pressure will be in control of our
weather through Thursday night yielding continued quiet
conditions across the region.

Synoptic northeasterly flow today will hold temperatures in the
mid 60s lakeside, while highs will warm into the upper 70s and
lower 80s inland. Forecast soundings depict a plume of very dry
air aloft centered around 750 mb (dewpoints near -30C). Fairly
deep PBLs today should allow for some mixing into the base of
this dry layer, and surface dewpoints will likely mix out a bit
in response to this (away from the immediate lake influence).
Have nudged Tds down a bit with this in mind which yields
afternoon RH values in the low 20s.

The surface high will wobble eastward on Wednesday and column
thicknesses will increase a smidge in response. Highs will jump
several degrees as a result, with lingering lake cooling
confined particularly to the northeast Illinois shore. Similarly
dry conditions to Tuesday may also develop, and it`s possible
some further reductions to dewpoints/RHs may be needed in future
grid updates.

Deeper southwesterly tropospheric flow will establish across the
region on Thursday. Attendant offshore flow will commensurately
push mid-upper 80 degree temperatures all the way to the
lakefront. A modest increase in boundary layer moisture may
yield a bit more diurnal cumulus development, as well as some
breezier southwesterly winds. At this time, the wind/RH combo
doesn`t quite look to rise to the level of an elevated fire
danger, but given how dry conditions have been, will need to
keep an eye on trends for Thursday afternoon.

A transition to an intermittently more showery/stormy period
will occur later Friday and through the upcoming weekend and
possibly into next week as large scale blocking breaks down. At
this time, it looks like the bulk of the day on Friday may
remain dry, although chances for showers and some thunderstorms
will increase during the afternoon, particularly west of the Fox
Valley. Otherwise, warm and breezy conditions are expected.

Given the break down of such a highly-amplified pattern, it`s
not surprising to see a pretty sizable spread in the handling
of the salient synoptic elements over the weekend and into next
week. Regardless, there is good agreement in a significant
increase in column moisture, particularly Friday night into
Saturday/Saturday night with PWATs at times forecast to near 2
inches. With several disturbances or bonafide shortwaves
traversing the area, this could yield periodic scattered showers
and storms, perhaps with heavier downpours at times.

It`s a bit unclear how the large scale pattern will evolve on
Sunday and into next week. The GFS and many of its ensembles
(and to some degree the CMC/GEPS) continue to suggest the
primary frontal zone will push well south of the region leading
to a reduction in moisture and precipitation chances, while the
ECMWF/EPS hold onto a somewhat stormier/active pattern in the
region. For now, the generally low-chance PoPs from the NBM seem
appropriate at this range given climatology and the ensemble
spread.

Carlaw

&&

.AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 632 AM CDT Tue Jun 2 2026

There are no key concerns for the 12Z TAF period.

Light NE winds early this morning will pick up to 10 to 12 kt
by mid morning before subsiding during the evening. Light winds
may go variable late tonight, but should favor NE through the
night before going SE by mid morning Wednesday. Expect VFR
throughout the period.

Doom

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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